A step down transformer converts a voltage of 2200 V into 220 V in the transmission line. Number of turns in primary coil is 5000. Efficiency of transformer is 90% and its output power is 8kW. Calculate (i) number of turns in secondary coil (ii) input power.

Explanation

Efficiency `eta = ("Outpur power")/("Input power")`
or Input power `= ("Output power")/(eta)`
`= (8)/(90//100) = 8.9 kW`
Again `(N_(S))/(N_(P)) = (E_(S))/(E_(P))` or `N_(S) = (E_(S))/(E_(P)) xx N_(P)`
Here `N_(P) = 5000, E_(S) = 220V`
`E_(P) = 2200 rArr N_(S) = (220)/(2200) xx 5000 = 500`